Server-sent events in PHP (without echo or print)

Question

We have built a prototype application in PHP and JS using Server-Sent Events (single AJAX requests, multiple streamed events sent by event handlers in PHP). Essentially the PHP at some point is using echo to send data back, much like this example: https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#sending_events_from_the_server i.e.

echo "event: ping\n";

However the platform we are building for (Magento) has strict coding standards that prohibit echo and print (and print_r and var_dump). Is there any way around this aside from scrapping SSE and setting up AJAX polling?

Answer 1

Well, I think you have 2 ways of "echoing" something in Magento.

1. Adding your PHP file to /pub

Yes, you can run you custom PHP file to "echo" whatever you want. But you will need to place it under <magento folder>/pub/yourfile.php.

If you're using nginx you will also need to create an exception for your file. Otherwise, Magento's routing will be used.

For doing that, find something like location ~ ^/(index|get|static|errors/report|errors/404|errors/503|health_check)\.php$ { in your nginx file, and add yourfile.php there.

For example:

location ~ ^/(index|get|static|errors/report|errors/404|errors/503|health_check|yourfile)\.php$ {.

Once your file is there, it will be served under yourstore.com/yourfile.php or yourstore.com/pub/yourfile.php (in case you are wrongfully exposing the root directory).

2. The magento way - create a controller

You will need to create a module and a controller. There are plenty of tutorials out there explaining how to create them.

Here you can find how to create the basic module's structure.

And in this other article you can see how to create different controllers with different types of return.

Answer 2

Magento does have strict standards as part of there PHPCS configuration that need to be adhered to before they will allow you publish a module to there market, there is not Solid fix for the issue you have mentioned regarding using echo or print in a magneto file as part of your module. however we have found a work around by leveraging phps Output Buffering.

We have successfully submitted a module using the below mentioned function and example.

You can use ob_start() and ob_end_flush() it behaves similar to how a print or echo would when interacting with the event stream. See link below for example.

Why?

The ob_flush() function outputs the contents of the topmost output buffer and then clears the buffer of the contents. The output may be caught by another output buffer or, if there are no other output buffers, sent directly to the browser ( IE. your currently open stream ).

Example:

   /**
     * Send Data
     *
     * @param string $content
     */
    function sseEchoAlternative(string $content)
    {
        ob_start(function () use ($content) { //Expect a warning here
            return $content;
        });
        ob_end_flush();
    }

Ref: ServerSentEvents.php